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本文研究了二茂钛含氟长链有机酸衍生物(1~3)和具有环状结构的新型二茂钛全氟有机酸(4~7)的电子轰击质谱(EIMS)和负离子化学电离质谱(NICIMS)。在EI谱中出现弱的或不出现M~+,1~7均以CpTiF_2离子为基峰。高质量区的主要特征碎片离子有[M-·cp]~+、[M-R]~+(1~3)和氟重排离子。在低质量区出现一系列二茂钛及茂钛氟重排离子。 1、4~7的NICI(CH_4)质谱中,4、5出现强的M~-离子峰,1出现[M-1]-离子峰,有两个钛的环状结构化合物6和7出现双电荷M~=离子峰,而不出现M~-。 相似文献
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分子的电离电势、键能和离子的标准生成焓等都是非常重要的物理化学数据,它们对化学反应机理等研究有很大帮助,精确测定离子的出现势,就可以获得这些热力学常数.迄今为止,有关溴乙烷(C2H5Br)电离解离过程的研究已有若干报导[1-3],但这些结果均是在常温条件下,用电子轰击电离、彭宁电离或真空紫外灯辐照等方法获得的,由于常伴有热带效应、离子分子反应、离子对形成等过程[4],其结果的准确性往往较差.本文首次报导使用同步辐射光源对C2H5Br进行光电离解离研究.通过准确测量母体离子以及几种主要碎片离子的出现势,结合已有的公认的热力… 相似文献
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甲烷和二氯甲烷混合反应气体的负离子化学电离质谱,对多肽和核苷等极性有机化合物的分析能提供有关[M+Cl]-离子和分子结构的信息,并可减轻单纯使用二氯甲烷作反应气体时对灯丝的损害程度。本文研究了该方法的实验条件、分析结果和局限性。化学电离源质谱法,甲烷,二氯甲烷,寡肽。 相似文献
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理论计算非常适用于气相离子化学研究[1,2],它与质谱实验相结合可以识别许多非常规的和以往所不知道的自由基离子,也可以提供反应能和机理方面的信息,有助于探讨可能的异构化过程和不同异构体结构的相对稳定性.离子/中性复合物(离子和中性碎片通过静电引力结合在一起)[3]作为有机离子质谱单分子碎裂的重要中间体已被越来越多的理论和实验结果所证实[3,4].串联质谱低能碰撞诱导解离和同位素标记技术的实验结果表明[5]:四氢咪唑取代亚甲基β-二酮分子结构中氮原子上氢表现出不同活性,其气相单分子碎裂经历了离子/中性复合物的中… 相似文献
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稀土硝酸盐与1,1,1-三(4′-二苯胺甲酰基-2′-氧杂丁基)丙烷配合物的合成及谱学性质 总被引:3,自引:0,他引:3
三角架型配体由于其独特的配位方式而具有许多优良的物理和化学性质 ,如能稳定高氧化态的过渡金属离子[1 3] ,用作优良的电极活性物质[4] ,具有生物活性[5] 等 .因此近十余年来对该类配合物的研究一直是配位化学研究领域的一个重要部分 .但到目前为止 ,对具有三角架结构的三酰胺型开链冠醚的研究却很少 ,且主要集中于研究它与过渡金属和碱金属离子的相互作用及其性质[4,5] ,有关该类配体与稀土离子的配位形式及性质的研究则更少[6] .为了进一步研究该类配体与稀土离子的配位能力及所形成配合物的性质 ,我们参照文献 [5]方法 ,合成出配体 1 ,… 相似文献
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采用50~200nm同步辐射光,对CH2Br2的光电离过程进行了研究,根据测定的母体离子及其碎片离子出现势,得到二溴甲烷的绝热电离势为10.23±0.01eV,并获得了离子的生成焓,解离能及键能等热力学数据,分析了碎片离子的光解离电离通道。 相似文献
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Chromatographic and mass spectral studies of perfluorooctanesulfonate and three perfluorooctanesulfonamides 总被引:2,自引:0,他引:2
The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen-substituted perfluorooctanesulfonamides have been obtained. A methyl/phenyl mixed-phase fused-silica capillary column was used for gas chromatographic (GC) analyses, while a C18 reversed-phase microbore column was used for liquid chromatographic (LC) analyses. Mass (MS) and tandem mass (MS/MS) spectra were generated using electron ionization (EI), argon CE, methane positive and negative ion CI, and ES ionization modes. EI spectra of the amides showed ions characteristic of both the fluorinated hydrocarbon and the sulfonamide portion of the molecules. The fragmentation pathway was studied using hydrogen/deuterium exchange, and was thought to involve a cyclic intermediate ion. Formation of molecular ions by CE and protonated molecule ions by CI to obtain molecular weight information was only partially successful. Negative ion ES-MS spectra provided intense [M-H]- anions for the amides, and an [M-K]- anion for PFOS from which molecular weight information could be obtained, while ES-MS/MS produced product ions that could be used to detect the presence of these compounds in biological or environmental samples. 相似文献
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Kolárová L Holcapek M Jambor R Dostál L Nádvorník M Růzicka A 《Journal of mass spectrometry : JMS》2004,39(6):621-629
Electrospray ionization (ESI) mass spectrometry was applied to the structural analysis of 23 2,6-[bis(alkyloxy)methyl]phenyltin(IV) derivatives. The mass spectra were measured in both polarity modes and multistage tandem mass spectrometric (MS(n)) measurements were performed on the ion trap analyser for positively charged tin-containing ions. The sum of complementary ions observed in the positive-ion mode (i.e. [M-R(3)](+) ion) and in the negative-ion mode (i.e. [R(3)](-) ion) permits molecular mass determination in spite of the fact that the molecular adducts were often missing even in the first-order mass spectra. The subsequent fragmentation of [M-R(3)](+) ions studied by MS(n) and the correlation of observed fragment ions with the expected structures of synthesized organotin(IV) compounds allowed us to understand the fragmentation behaviour and the mechanism of the ion formation for studied compounds. The typical neutral losses are alkenes, alcohols and aldehydes. The fragmentation pattern of one selected compound was supported by MS(n) measurements of an isotopically labelled analogue to confirm unusual ion-molecule reactions of some fragment ions with water in the ion trap. 相似文献
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采用电喷雾-离子阱质谱(ESI-IT MS),获取大黄酸分子的一级质谱和多级质谱碰撞诱导解离下的碎片离子,以量子化学计算大黄酸分子及其主要碎片离子的质谱行为。通过对质谱离子几何参数、键断裂能、电荷变化、自旋密度以及前线分子轨道的分析,可得到m/z 282.8、256.9、238.9、210.8、192.8、182.8、166.8离子的稳定构型以及质谱裂解途径,从而较系统地解释了大黄酸分子在ESI-IT MS中的裂解行为。 相似文献
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Oligosaccharides were derivatized by reductive amination using benzylamine and analyzed by nanoelectrospray ionization-quadrupole time of flight-tandem mass spectrometry (nanoESI-QTOF-MS/MS) in the positive ion mode. The major signals were obtained under these conditions from the [M+H]+ ions for all benzylamine-derivatized oligosaccharides. To obtain structural information from these derivatized oligosaccharides, MS/MS was applied. Protonated molecular ions underwent extensive fragmentation, even under low-energy collision-induced dissociation. MS/MS spectra of [M+H]+ ions are characterized by simple fragmentation patterns which result from cleavage of the glycosidic bonds and thus allow a straightforward interpretation. Fragmentation of the [M+H]+ ions gave predominantly B- and Y-type glycosidic fragments. A systematic study of various oligosaccharides showed that information on sugar sequence and branching could easily be obtained. Predictable and reproducible fragmentation patterns could be obtained in all cases. This derivatization procedure and mass spectrometric methodology were applied successfully to neutral and acidic glycans released from 10 microg of glycoproteins separated by gel electrophoresis. Moreover, the derivatives retain their sensitivity to exoglycosidases. Thus a series of sequential on-target exoglycosidase treatments combined with matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) was found to be useful for the determination of structural features of the glycans released from proteins separated by gel electrophoresis such as the monosaccharide sequence, branching pattern, and anomeric configurations of the corresponding glycosidic linkages. Our strategy can be used successfully to assign the major glycans released from proteins separated by gel electrophoresis. 相似文献
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Taguchi VY 《Rapid communications in mass spectrometry : RCM》2001,15(7):455-461
Two unusual disinfection by-products have been detected periodically in the gas chromatography/mass spectrometry (GC/MS) characterization analyses of semi-volatile organics in treated drinking water. The electron ionization (EI) mass spectra contained mono-chlorinated and mono-brominated ions at m/z 107/109 and 151/153, respectively. Library searching techniques suggested mono-halogenated butanol structures but no matches could be found. Positive ion chemical ionization (CI) spectra contained mono-chlorinated and mono-brominated ions at m/z 105/107 and 149/151, respectively. No [M + H]+ ions were initially observed. Accurate mass measurements confirmed the empirical formulae for the significant ions in the EI spectra and the mono-halogenated butanol structures. Further CI experiments with other reagent gases and instruments revealed possible molecular weights of 139 and 183 Da, respectively. Tandem mass spectrometry (MS/MS) experiments in EI and CI were used to elucidate the fragmentation schemes. The two compounds have been tentatively identified as 1-aminoxy-1-chlorobutan-2-ol and 1-aminoxy-1-bromobutan-2-ol, respectively. 相似文献
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Two mass spectrometers, in parallel, were employed simultaneously for analysis of triacylglycerols in canola oil, for analysis of triolein oxidation products, and for analysis of triacylglycerol positional isomers separated using reversed-phase high-performance liquid chromatography. A triple quadrupole mass spectrometer was interfaced via an atmospheric pressure chemical ionization (APCI) interface to two reversed-phase liquid chromatographic columns in series. An ion trap mass spectrometer was coupled to the same two columns using an electrospray ionization (ESI) interface, with ammonium formate added as electrolyte. Electrospray ionization mass spectrometry (ESI-MS) under these conditions produced abundant ammonium adduct ions from triacylglycerols, which were then fragmented to produce MS/MS spectra and then fragmented further to produce MS/MS/MS spectra. ESI-MS/MS of the ammoniated adduct ions gave product ion mass spectra which were similar to mass spectra obtained by APCI-MS. ESI-MS/MS produced diacylglycerol fragment ions, and additional fragmentation (MS/MS/MS) produced [RCO](+) (acylium) ions, [RCOO+58](+) ions, and other related ions which allowed assignment of individual acyl chain identities. APCI-MS of triacylglycerol oxidation products produced spectra like those reported previously using APCI-MS. APCI-MS/MS produced ions related to individual fatty acid chains. ESI-MS of triacylglycerol oxidation products produced abundant ammonium adduct ions, even for those molecules which previously produced little or no intact molecular ions under APCI-MS conditions. Fragmentation (MS/MS) of the [M+NH(4)](+) ions produced results similar to those obtained by APCI-MS. Further fragmentation (MS/MS/MS) of the diacylglycerol fragments of oxidation products provided information on the oxidized individual fatty acyl chains. ESI-MS and APCI-MS were found to be complementary techniques, which together contributed to a better understanding of the identities of the products formed by oxidation of triacylglycerols. 相似文献
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H. I. Kenttämaa 《Journal of mass spectrometry : JMS》1985,20(12):703-714
Dramatically different fragmentation patterns are obtained for 4-ethyl-2,6,7-trioxa-1-phosphabicyclo-[2.2.2]octane-1-oxide upon electron ionization (EI) and for the corresponding molecular ion on collision-induced dissociation (CID). Two reasons for this behaviour have been discovered. (i) Irreversible multistep isomerization of the molecular ions occurs prior to collisional activation in mass spectrometry/mass spectrometry (MS/MS). Isomerization reactions have been characterized by isotopic labelling and by examining structures of relevant unlabelled and labelled fragment ions by MS/MS. The extent of isomerization can be controlled by varying the amount of internal energy of the molecular ions. This has been done by changing the number of thermalizing collisions which the ions undergo with neutral molecules in the ion source. (ii) When multiple collisions are used to dissociate the molecular ions, the initially stable fragmentation products undergo extensive further decomposition. As a result, abundant phosphorus-containing fragment ions are obtained for the bicyclic phosphate in high-pressure CID, whereas electron ionization leads to predominant hydrocarbon ions. A minor change in the structure of this molecule has major effects on the fragmentation behaviour: high- and low-energy collisional activation spectra of the molecular ion of the corresponding phosphite are identical with the 12 e V EI mass spectrum of the neutral. 相似文献
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Raska CS Parker CE Huang C Han J Glish GL Pope M Borchers CH 《Journal of the American Society for Mass Spectrometry》2002,13(9):1034-1041
Both the matrix selected and the laser fluence play important roles in MALDI-quadrupole/time of flight (QqTOF) fragmentation processes. "Hot" matrices, such as alpha-cyano4-hydroxycinnamic acid (HCCA), can increase fragmentation in MS spectra. Higher laser fluence also increases fragmentation. Typical peptide fragment ions observed in the QqTOF are a, b, and y ion series, which resemble low-energy CID product ions. This fragmentation may occur in the high-pressure region before the first mass-analyzing quadrupole. Fragment ions can be selected by the first quadrupole (Q1), and further sequenced by conventional MS/MS. This allows pseudo-MS3 experiments to be performed. For peptides of higher molecular weight, pseudo-MS3 can extend the mass range beyond what is usually accessible for sequencing, by allowing one to sequence a fragment ion of lower molecular weight instead of the full-length peptide. Peptides that predominantly show a single product ion after MS/MS yield improved sequence information when this technique is applied. This method was applied to the analysis of an in vitro phosphorylated peptide, where the intact enzymatically-generated peptide showed poor dissociation via MS/MS. Sequencing a fragment ion from the phosphopeptide enabled the phosphorylation site to be unambiguously determined. 相似文献
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Domingues MR Domingues P Gajewski M Czuchajowski L Ferrer-Correia AJ 《Rapid communications in mass spectrometry : RCM》2001,15(12):908-914
Several compounds, representative of the class of lexitropsins, were analyzed by electrospray tandem mass spectrometry. The study of the fragmentations of the protonated molecular species ([M + H](+)) and of selected fragment ions allowed proposals for the main fragmentation pathways of compounds of this type. The interpretation of the fragmentation pathways of these compounds was complicated because of intramolecular hydrogen migration. In order to better understand the fragmentation pathways, the MS/MS/MS spectra of several compounds, and the MS/MS and MS/MS/MS spectra of the deuterated compounds, were obtained. Accurate mass measurements helped elucidate the structures of smaller fragment ions. Low-energy collision-induced decomposition (CID) tandem mass spectrometry of lexitropsins with electrospray ionization has proven to be a good method for the structural characterization and identification of this class of compounds. Main fragmentation pathways occur by cleavage of the peptide bond followed by the elimination of the substituted pyrrole ring, and their elucidation will facilitate structural characterization of new lexitropsins. 相似文献